Perforation detector for continuous webs



A ril 25, 1967 J. 5. LINDERMAN 3,316,411

PERFORATION DETECTOR FOR CONTINUOUS WEBS Filed June 18. 1965 2 Sheets-Sheet 1 FIG.!

FIG.2

INVENTOR JAMES STEPHENS LlN-DERMAN ATTORNEY Ap l 5, 1967 J. 5. LINDERMAN PERFORATION DETECTOR FOR CONTINUOUS WEBS 2 Sheets-Sheet 2 Filed June 18, 1963 5:: 2%" .55 52E: 5%: :35 ,5, 2:23am .s. R i E K 1.2 E n u 2:26: 5.83 TAIIII INVENTOR JAMES STEPHENS LINDERMAN ATTORNEY United States Patent Office 3,316,41 l Patented Apr. 25, 1967 3,316,411 PERFORATION DETlwTgR FOR CONTINUGUS E James Stephens Linderman, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed June 18, 1963, Ser. No. 288,766 4 Claims. (Cl. 250-219) This invention relates to light-sensitive devices and more particularly, it relates to a device for detecting imperfections in the perforations along a continuous web. Still more particularly, the invention relates to a device for detecting either missing perforations, elongated perforations or weaving perforation track.

Continuous webs are frequently provided with apertures or perforations along one or both sides, for example, cine perforations which are placed on picture film. Depending on the type of perforator used, various defects may be produced in the perforations or between the perforations; for example, if the motion of the film is inadvertently slowed or stopped, there is a tendency for the perforator to cut elongated perforations, even to the extent of triple the desired length or longer; or the perforation track may occasionally tend to weave back and forth across the lateral width of the film; or incomplete punching may result in missing perforations.

Since most modern perforating devices operate at high speeds on continuously moving film, it is desirable to have an inspection device capable of continuously inspecting the film and determining perforation defects. Such a device should be sensitive to any and preferably all of the defects enumerated above and be capable of actuating either an audible or visible alarm responsive thereto. Since the perforating operation, and the detection of defects therein, are frequently to be conducted on unexposed photographic film, any device employed for this purpose must be one which will not expose or harm the emule sion layer.

These and other objects are accomplished in accordance with this invention which is particularly pointed out in the appended claims and is illustrated, in its preferred embodiments, in the accompanying drawings wherein:

FIGURE 1 is a schematic illustration of a preferred device constructed in accordance with this invention.

FIGURE 2 is a view of a portion of a defectively perforated film having an elongated perforation.

FIGURE 3 is a view of a portion of a defectively perforated film having a missing perforation.

FIGURE 4 is a schematic diagram of the electrical circuit employed in the invention.

FIGURE 5 is a view of only the elements 16 and 17 of FIGURE 1 showing an alternative embodiment of the invention.

FIGURE 6 is an enlarged fragmentary view of element 17 of FIGURE 5 with the perforation track shown projected thereon.

Referring now to the drawings, FIGURE 1 shows a light bulb 10 generally directing a light beam through filter 11 which removes that portion of the light which will expose the particular film being inspected and a light collimating device 12 such as a Fresnel lens. All the latter elements are located within the housing 13 which has four 150 mil diameter apertures 1441-51. Light beams ISa-d are produced and directed toward the perforated web 16 along its perferation tracks. Located beneath the web 16 is a plate 17 containing two pairs of accurately milled slits 18a and b and 19a and b. For use in connection with single or doub e perforated 16 mm. cine film, these slits are 10 mils wide and approximately 120 mils in length, each pair being matched to better than 0.2 mil both as to width and as to length, and spaced apart from one another along the film path by 300.0i0.1 mil. Two pairs of detectors 20a and b and 21a and b are located below their corresponding pairs of slits. An electrical impulse is transmitted from each detector when light is incident thereon. The impulses from detectors 20a and b are transmitted to an exclusive or circuit 22 (coincidence circuit). In the latter the separate electrical impulses are compared as to presence and if both are present or both are absent, no electrical output signal is transmitted from circuit 22 to standard or circuit 23. But, if either is absent, a signal is transmitted to circuit 23, from which a signal is then transmitted to the alarm 24. Additionally, if either pulse is seriously misshaped or reduced in magnitude, such an occurrence is also interpreted as cause for actuation of the output circuit and, consequently, the alarm. The alarm can be of either the audio or visual type and many suitable alarms will be apparent to those skilled in the art. The electrical impulses transmitted -by detectors 21a .and b are handled in exactly the same manner by exclusive or circuit 25, standard or circuit 23 and alarm 24, standard or circuit 23 being activated by a signal from either or both circuits 22 or 25.

Thus, in the device described in FIGURE 1, if a defective fil-m 30 of the type shown in FIGURE 2 (having an elongated perforation 31) were being inspected light beams 15c and d would pass through perforations 32 and 33, slits 19a and b and strike detectors 21a and b. Since perforations 32 and 33 are of perfect size and spacing, the movement of the web in the direction of the arrow shown in FIGURE 1 would cause light beams 15c and d to be alternately transmitted or obstructed simultaneously. In such a case, detectors 21a and 21b would either be simultaneously receiving light or simultaneously obscured; therefore, there would be no difference in the impulses transmitted to exclusive or circuit 25 from detectors 21a and 21b and no output signal would emanate therefrom. However, in the case of light beams 15a and b, while they would both be simultaneously transmitted through the extremities of elongated perforation 31, continued movement of the film would cause light beam 15b to be obscured while 15a 'was not. The result would be that detector 29a would be receiving light and transmitting an impulse to exclusive or circuit 22 while detector 20b was not. This unbalance would be detected by exclusive or circuit 22 and cause the transmission of an output signal therefrom through circuit 23 to activate the alarm 24.

In the case that a film having a missing perforation as shown in FIGURE 3 would pass through the device, again no defect would be noted by detectors 21a and 21b since light beams 15c and d would be simultaneously either obscured or transmitted. However, as the film is advanced in the direction of the arrow until light beam 15a passes through perforation 34, light beam 15b would be obscured owing to the missing perforation. This would cause an impulse to be transmitted by detector 20a. with no synchronous impulse emanating from detector 20?). Again, the unbalance would cause the output signal from circuit 22 to actuate the alarm 24.

The electronic circuitry for the device is shown in FIGURE 4, and is largely mounted on a single printed circuit card. Detectors 20a, 20b, 21a and 21b are represented as four FSP-S phototransistors (manufactured by Fairchild Semiconductor Corp.). The arms of two 25K ohm potentiometers are brought out respectively to points I and F on a terminal strip of the printed circuit card to provide for initial adjustment of the circuit to balance. With respect to the upper pair of detectors 20a and 20b, at circuit balance, the voltage at point I will always be the same either if light beams 15a and 15b are both totally obscured or if both strike the detectors simultaneously causing the individual resistances to change equally.v However, if only one of the two light beams strikes its detector the resistance will only decrease in the former and, therefore, the voltage balance at point I will be altered. Similarly, if one light beam is changing its value more or less rapidly'than its mate, as by one perforationedge slightly leading its mate, the voltage 'from standard or circuit 23 to the base of transistor 43 which is initially biased off. Once this positive signal going to the base of transistor 43 causes it to turn on,

the signal is amplified and fed to the base of transistor 44 which is also initially biased off. The latter signal however, causes it to go into conduction thereby supplying current to the coil of relay 45 and activating alarm 24. Closing of the relay terminals causes a current from transistor 44 to be fed back through pin E and the 220K resistor into'the base of transistor 43 thereby latching it into continued operation. The relay may 'be reset and I the alarm deactivated by breaking the feed-back from the transistor 44 to the base of transistor .43; reset .pushbutton 46 is provided for this purpose.

Unequal activation of detectors 21a and 21b are handled by exclusive or circuit 25 in the same manner, the effect being to permit the alarm to be activated by defects which are noted oneither or both sides of the perforation track.

A device as described is theoretically capable of detecting even minutedifferences in the light beams striking one pair of detectors;-variation in the detection sensitivity may be accomplished by regulating the size of slits 18a, 18b, v19a, and 1%.. At the stated width of mils, a variation of perforation positionlengthwise of less than /2 this width is enough to activate the system. This sensitivity enables: the detection of less than a 10 percent elongation in individual perforations up to film speeds up to 400 feet per minute. By widening the slit width to more than 10 mils, this sensitivity may be decreased.

In addition, a weave in the perforation track (in excess of'8 mils/perf. pitch) can be detected by the device. .As illustrated in FIGURES 5 and 6, one of the'slits (18a of FIG. 1) is replaced by a pair of rectangles 18c and 18d spaced apart transversely of the direction of filmtravel; the spacing is slightly less than a perforation width, and the center of the spacing is located on the center line of the perforations in the proper path, i.e., when not weaving The other slit 18b is formed as another rectangle the width of which is equal to the perforation width; this rectangle is centered on the center line of the perforations in their proper path, asabove. The dimen sion of the rectangles in the film travel direction is sufficient so that enough light is passed when one of the pair of rectangles is completely out off, or the single rectangle is approximately half cut off, justto actuate the alarm system.

In operation, weaving of the perforations away from "their proper path has no efiect on the total'amount of light passing through the paired rectangles 18c and 18d,

because as less light passes through one, more passes through the other and the total light passing the pair remains unchanged. However, weaving of the perforations,

as they pass the single rectangle. 18b causes a reduction in the light passing through this rectangle. When the weaving is so severe as to cut off more than half the light from this rectangle, the voltage unbalance in the exclusive or circuit 22 is suflicient to actuate the alarm.

Although this device has been described in connection with its use in testing. 16 mm. cine film, it will be clear that it is within the skill of the art to shift the dimenoccur in uniformly positioned pairs or multiples.

What is claimed is:

1. .A device for determining the presence and relative variation of each one of desired, multiple, aligned apertures in a web and the absence of undesired apertures, which device comprises a light source located on one side of said web for directing collimated light at said web apertures, a pair of light detectors located at a multiple of the aperture spacing on the opposite side of said web for simultaneously delivering separate electrical impulses responsive to the detection oflight transmitted through adjacent apertures incident on said detectors, and sensing means for sensing the non-coincidence and variation between said electrical impulses.

2. A device for determining the presence and relative longitudinal variation of each one of desired, multiple, uniformly-spaced, aligned perforations along a continu ously moving film perforated in a track along its edge and the absence of undesired perforations, which device comprises means for directing a pair of collimated light beams along the perforation track of said film, a pair of narrow parallel slits, a pair of light detectors located on the opposite side of said film which receive the light transmitted through said perforations and slits and deliver separate electrical impuises upon detection of said light, the members of said pairs being spaced along the track at a multiple of the perforation spacing to provide simultaneous light reception by said light detectors, sensing means'for sensing the non-coincidence and variation between said impulses and delivering an electrical output responsive thereto, and alarm means responsive to said.

' track of said film, a pair of narrow parallel slits located beneath each'track on the opposite side of said film, a pair of light detectors beneath each pair of slits which receive the light transmitted through said perforations and slits and deliver separate electrical impulses upori detection of said light, the members of said pairs being spaced along said tracks at a multiple of the perforation spacing to provide simultaneous light reception by said light detectors, separate sensing means for each pair of detectors fo'rsensing the non-coincidence and variation between said impulses and delivering an electrical output responsive thereto, and alarm means responsive to said electrical output transmitted from said sensing means.

4. A device for determining abnormal relative transverse variation of each one of desired, multiple, uniformly-spaced, aligned perforations along a continuously moving film perforated in a track along its edge, which device comprises means for directing a pair of light beams along the perforation track of said film, a plate located on the opposite side of said film, said plate having a first opening of a width equal to the width of a perforation and being centered on the perforation track, said plate having a pair of second openings transversely aligned on either side of said perforation track being separated by a space of less than the width of a perforation,

5 6 said first opening being spaced from said second openings References Cited by the Examiner along the track at a multiple of the perforation spacing, UNITED STATES PATENTS a pair of light detectors which receive the light trans- 2,203,706 6/1940 Stockbarger 25O 219 mitted through said perforations and openings and de- 2,994,783 8/1961 Looschen 250 219 liver separate electrical impulses upon detection of said 5 light, sensing means for sensing the non-coincidence and variation between said impulses, and alarm means respon- RALPH NILSON Primary Examiner sive to said electrical output transmitted from said sens- WALTER STOLWEIN, Examinering means. 10 M. A. LEAVI'IT, Assistant Examiner.

3,131,332 4/1964 Guri 250-210 X 

3. A DEVICE FOR DETERMINING THE PRESENCE AND RELATIVE LONGITUDINAL VARIATION OF EACH ONE OF DESIRED, MULTIPLE, UNIFORMLY-SPACED, ALIGNED PERFORATIONS ALONG A CONTINUOUSLY MOVING FILM PERFORATED IN TWO TRACKS, ONE TRACK ALONG EACH EDGE OF SAID FILM, AND THE ABSENCE OF UNDESIRED PERFORATIONS, WHICH DEVICE COMPRISES MEANS FOR DIRECTING A PAIR OF COLLIMATED LIGHT BEAMS ALONG EACH PERFORATION TRACK OF SAID FILM, A PAIR OF NARROW PARALLEL SLITS LOCATED BENEATH EACH TRACK ON THE OPPOSITE SIDE OF SAID FILM, A PAIR OF LIGHT DETECTORS BENEATH EACH PAIR OF SLITS WHICH RECEIVE THE LIGHT TRANSMITTED THROUGH SAID PERFORATIONS AND SLITS AND DELIVER SEPARATE ELECTRICAL IMPULSES UPON DETECTION OF SAID LIGHT, THE MEMBERS OF SAID PAIRS BEING SPACED ALONG SAID TRACKS AT A MULTIPLE OF THE PERFORATION SPACING TO PROVIDE SIMULTANEOUS LIGHT RECEPTION BY SAID LIGHT DETECTORS, SEPARATE SENSING MEANS FOR EACH PAIR OF DETECTORS FOR SENSING THE NON-COINCIDENCE AND VARIATION BETWEEN SAID IMPULSES AND DELIVERING AN ELECTRICAL OUTPUT RESPONSIVE THERETO, AND ALAEM MEANS RESPONSIVE TO SAID ELECTRICAL OUTPUT TRANSMITTED FROM SAID SENSING MEANS. 